Chemiluminescence is achieved by a reaction of two or more chemicals to create light. One class of chemiluminescence is based on a peroxide-oxalate reaction using a mixture of hydrogen peroxide with an oxalate and a dye dissolved in a suitable solvent. Hydrogen peroxide reacts with the oxalate to produce an unstable strained ring peroxyacid ester intermediate (i.e., 1,2-dioxetanedione), which in turn decomposes spontaneously to carbon dioxide releasing energy that excites the dye. As the excited dye returns to its ground state, a photon of light is released.
Most commercially-available “glow sticks” utilize this peroxide-oxalate reaction and can produce light for over 6 hours in a wide variety of colors. The structure of the dye determines the wavelength of light emitted. Exemplary dyes used in glow sticks include 9,10-diphenylanthracene to create blue light, or rhodamine B to create red light. Advancements in glow stick chemistry have generally focused on extending the lifetime of the chemical reaction, increasing its brightness, or creating new colors.
In U.S. Pat. No. 8,137,597, which is incorporated herein by reference in its entirety, a one-part, pressure activated chemiluminescent material suitable for micro-scale application is disclosed, where a free-flowing powder is made by coating microcapsules, which are filled with a solvent and dye, with a powdered oxalate and a solid source for hydrogen peroxide. The formation of the microcapsules comprising the solvent and dye is a chemical encapsulation involving a complex coacervation technique, in-situ microencapsulation technique, or an interfacial microencapsulation technique. The chemiluminescence reaction begins when the capsules are crushed. The fractured microcapsule releases the solvent, which dissolves both the oxalate and the hydrogen peroxide source, and the concomitant solution phase reaction between the dissolved solids (i.e., oxalate and peroxide) releases energy that excites the dye to produce the chemiluminescent light.
Investigations into the known methods of making and packaging the reactants have revealed that the micro-capsules obtained by the complex coacervation technique may entrain a small quantity of water droplets within the core of the capsule. The entrained water can slowly degrade one or more of the reactants and thereby shorten the shelf-life of this chemiluminescent material.
Accordingly, new chemiluminescent materials and manufacturing methods are needed.